The invention relates to an electric watch comprising a metal frame, a plastic frame, a stepping motor including a rotor and a stator with an associated coil, and a watch movement driven by the rotor of the stepping motor, wherein wheels of the watch movement and the rotor are arranged in bearing holes of these frames.
In the assembly of such watches, the standard procedure is to first insert one shaft end of various wheels of the watch movement and also one shaft end of the rotor--more strictly speaking: the rotor arrangement--of the stepping motor into the bearing holes of the metal frame provided for this purpose, and to then position the plastic frame on the thus obtained arrangement in such a way that the respective other shaft ends of the wheels of the watch movement and of the rotor enter the bearing holes of the plastic frame provided for this purpose. The plastic frame is then usually screwed to the metal frame, with the spacing between plastic frame and metal frame generally being determined by spacers which are already fixedly connected to the metal frame during assembly and which are provided at their free end with a threaded bore. In this way, the respective wheels of the watch movement, the rotor and, in accordance with the state of the art, also the stator of the stepping motor are secured in the desired position between the two frame elements.
Disadvantageous in the assembly of electric watches with the above-described frame construction is the occurrence between the permanent maget rotor and the magnetic stator of strong magnetic forces with the tendency to tilt the rotor in the direction of the fixed stator, whereby the free shaft end of the rotor is displaced in such a way that the plastic frame may no longer be readily positioned on the free shaft ends of the rotor. This renders assembly of the plastic frame more difficult and more expensive. There is also the danger that an assembler may press the plastic frame onto the shaft ends so that one or the other shaft becomes bent and/or one or several bearing holes are inadmissibly deformed, which means that the watch concerned has to be discarded later as a reject or repaired in a complicated manner, which increases the overall manufacturing costs accordingly.
One object underlying the invention is to so improve an electric watch of the type referred to above so that trouble-free assembly of the plastic frame is possible and the risk of assembly errors is reduced to a minimum.